There’s a lot involved in a successful irrigated pasture strategy
By Loretta Sorensen
Typically, when pasture is irrigated, forage receives adequate water at just the right time, forage quantity increases and grazing days can be extended. Harvesting all of those and even more benefits, though, involves much more than just turning on the water.
University of Nebraska-Lincoln (UNL) Professor of Agronomy/Extension Forage Specialist, Bruce Anderson, says maximizing the benefits of irrigated pasture begins with the types of forage selected. Since cool season grasses such as orchard grass, brome and fescue generally respond well to irrigation, they’re often the first varieties that come to mind in planning or establishing irrigated pastures.
“In the Great Plains, much of our existing pasture land, especially in areas of rangeland, consists primarily of summer grasses,” Anderson says. “Cool season grasses compliment summer grasses very nicely. But if you’re establishing or renovating an irrigated pasture, cool season grasses shouldn’t be the only grasses in the pasture.”
Anderson explains that irrigated pasture can be used to fill in grazing gaps that may occur later in the grazing season. If an abundance of cool season grasses is found in existing pasture, establishing summer grasses such as Big Bluestem and Indian grass, both of which respond well to irrigation, could be a valuable addition to a traditional pasture base.
“Cool season grasses peak earlier than the summer grasses,” Anderson explains. “When you’re adding both water and fertilizer to a pasture, you want to make sure your boost in grass production occurs at a time when you can get the most grazing out of it. A good general philosophy to keep in mind when you’re managing irrigated pasture is that growing more of what you don’t have is a good starting point in the planning process.”
A thorough inventory of forage found in existing pastures helps identify varieties that would supplement what’s already there and pinpoint which grass species would provide optimum production in the irrigated pasture location.
“Penciling out some options is a good way to determine what grasses best fit your specific needs,” Anderson suggests.
While maintaining adequate forage throughout the grazing season in 100% irrigated pasture is challenging, Anderson says it is possible. Even well watered, well-fertilized cool season grasses will not produce well in July and August temperatures.
“You probably only see about one-third of the amount of production from cool season grasses in July and August, compared to springtime, no matter how much water and fertilizer was used,” Anderson says. “That doesn’t mean all your pasture ground can’t be irrigated cool season grasses. It just means you need to plan to supplement grazing later in the season or stockpile some spring growth for summer use.”
One of the biggest mistakes Anderson has seen in irrigated pasture management is the tendency to overstock because anticipated forage production is unrealistic. This can be especially devastating in newly established pastures where grasses aren’t yet fully established.
“Irrigated pasture won’t produce to its maximum potential until the grasses are well established,” Anderson says. “It’s not unusual to see livestock producers overstock irrigated pasture because cool season grasses produce well in spring. During warmer months, forage production is greatly reduced.”
In order to reach maximum production from irrigated pasture, some type of fertilizer is almost always necessary. In planning the irrigated pasture, it’s important to allow for investing in the necessary inputs that allow the pasture to respond well to additional water.
“The amount of nitrogen provided for grasses in the irrigated pasture will be directly proportional to the quantity of grass you’re able to grow,” Anderson shares. “You also need to consider the cost of fencing and livestock water development, which are also necessary to effectively graze an irrigated pasture.”
UNL Professor of Agronomy and Horticulture/Soil Scientist-Crop Nutrition, Charles Shapiro, notes that grasses respond well to nitrogen inputs. Realizing the return on that investment is dependent on the use of the grass while nutritional content is high and before it matures into dry matter and goes to seed.
“If a pasture mix includes legumes, adding nitrogen could crowd out the legumes since legumes don’t respond to nitrogen as well as grasses do,” Shapiro says. “On warm season grasses, early nitrogen application will stimulate weeds and cool season grasses, and decrease warm season grasses.”
With fertilizer applications, if forage production isn’t increased and harvested, the cost of the fertilizer is wasted. If soil moisture conditions and other factors are not limiting, grassland can use a large amount of nitrogen. Where soils are sandy, fertilizing may not be economical. Timing of fertilizer application is important, since early fertilization of warm season grasses may stimulate weed growth. Both cool season and warm season grasses are typically fertilized later in the season.
“The biggest thing with fertilizing pasture or hay land is how to manage the flush of growth the fertilizer stimulates,” Shapiro notes. “Early in the grazing season, that growth may provide enough grass for 100 cows in the pasture. By August, grass production slows greatly and there may not be enough for those cows to eat.”
Balance the seasonal grasses
Irrigating pastures makes management of quick growth easier to manage because producers have greater control of the timing of the growth. However, making the most of the fertilizer investment requires careful management.
“Balancing the production of the cool season and warm season grasses is probably 80% of the challenge of managing irrigated pasture,” Shapiro adds.
In recent years, high grain prices coupled with rising pasture rental rates have pushed livestock producers to look beyond traditional grazing options. Recent drops in corn and soybean prices are causing grain farmers to reconsider how they’re using irrigated land, leading to some conversion of cropland to irrigated pasture.
“That was especially true when beef prices were still at record highs,” says Jerry Volesky, UNL Range Specialist, West Central Research and Extension Center. “Installing irrigation for pasture may not be as economic as converting irrigated cropland to pasture. That’s especially true if cropland is less productive due to low quality soils or rolling topography. Putting that type of land into pasture could work well.”
In central Nebraska, stocking rates on dryland pasture average 0.60 AUM (animal unit months). If pasture is irrigated and well managed, that stocking rate could increase between 10 and 12 times.
“It would take fertilizer application to get that maximum capacity,” Volesky explains. “But properly managing the irrigated pasture from the beginning, taking one or two years to get grasses well established, could greatly increase stocking rates.”
Ask your extension specialist
Extension and/or university range specialists can aid producers in grass variety selection. They can also provide insight into soil evaluations and identifying optimum planting conditions.
“April is typically a good month for spring planting and late August or early September are usually good times in Nebraska for fall planting,” Volesky says. “A quality drill set at the right depth for the grass variety being planted to ensure satisfactory seed-to-soil contact and a good, firm seedbed is important. That’s especially true with late summer seeding. If soil conditions are dry, make sure irrigation is used to keep the ground moist till seedlings get some growth on them.”
Irrigating grass seedlings after emergence is also key to effective establishment. A spring planting is typically easier to manage in terms of adequate moisture because temperatures are generally cooler.
“Overwatering is pretty difficult, but it could happen if there’s a heavy rain right after the pasture is irrigated,” notes Volesky. “If that occurs, it’s critical to monitor hoof action in the pasture to ensure there’s no area that gets muddied up because of all the moisture. With a high density stocking rate, there may be times when the cattle have to be pulled off the pasture until things dry up.”
In new pasture plantings, it’s normal to see a flush of weeds between two and three months after planting. Well-established pastures typically crowd out most weeds, although marestail and horse weed as well as Canadian and musk thistles can become problematic. Close monitoring of weed species and populations are the best guide to if, when and how weeds might be treated.
Keeping irrigation costs down can be accomplished with limited irrigation, reducing the amount of water applied during the hottest months when grass isn’t likely to respond to irrigation water.
“If you’re planning to use a limited irrigation strategy, you may consider mixing intermediate wheat grasses, which are very drought tolerant,” Volesky suggests. “During dry periods, intermediate wheat grasses will go dormant, but they won’t die out.”
Use of a flexible stocking rate can help in managing a growth flush and less productive cycles of the grazing season. That could be accomplished with a mobile fencing system used to create as few as four or five paddocks cattle rotate through. Providing a rest period for grazed areas gives grasses time to recover and regrow. Documenting forage production, stocking rates and irrigation water usage is important to an accurate assessment of the irrigated pasture’s success.
“Corn farmers calculate the bushel-per-acre every field makes because it’s so important to their understanding of profitability and production success,” Volesky says. “It’s just as important to maintain records related to the amount of rainfall received, amount of irrigation water applied and how much fertilizer was used. You’ll also want to know how many grazing days you realized from that pasture. All that information will useful in planning subsequent years.”
Over time, irrigated pastures may decline, much as an alfalfa field does. Grasses may thin out or disappear and patches of bare ground may appear and continue to enlarge.
“Eventually, it will be time to renovate the pasture,” Volesky says. “Getting the full value out of irrigated pasture is the biggest challenge. That requires careful monitoring and a flexible grazing strategy, but it can be a very economic way to use land.”
More detail about fertilizing pasture and hay land can be found at http://extensionpublications.unl.edu/assets/pdf/ec155.pdf.